1. Technical Field
The embodiments herein generally relate to communication networks, and, more particularly, to Orthogonal Frequency Division Multiplexing (OFDM) symbols of multi-media data transmission based on the MediaFLO™ (Forward Link Only) mobile multimedia multicast system.
2. Description of the Related Art
In recent years, the wireless industry has seen explosive growth in device capability, especially in relation to mobile devices, such as cell phones, handhelds, gaming consoles, etc. Ever-increasing demand for computing power, memory, and high-end graphic functionalities has accelerated the development of new and exciting wireless services. In the last few years, multiple technologies have been proposed to address delivery of streaming multimedia to mobile devices.
Multimedia communications provide a rich and immediate environment of image, graphics, sound, text and interaction through a range of technologies. An example of multimedia communication is streaming multimedia which is primarily a delivery of continuous synchronized media data. The streaming multimedia is constantly received by, and displayed to an end user while it is being delivered by a provider. Multiple technologies such as Integrated Services Digital Broadcasting-Terrestrial (ISDB-T), Terrestrial-Digital Multimedia Broadcasting (T-DMB), Satellite-Digital Multimedia Broadcasting (S-DMB), Digital Video Broadcasting-Handheld (DVB-H), and FLO (Forward Link Only) are used to address the delivery of streaming multimedia to mobile devices. These technologies have typically leveraged upon either third generation cellular/PCS, or digital terrestrial TV broadcast technologies.
For delivering unprecedented volumes of high-quality, streaming or clipped, audio and video multimedia to wireless subscribers, an air interface has been developed based on FLO technology for MediaFLO™ mobile multimedia multicast system available from Qualcomm, Inc., California, USA. MediaFLO™ or media forward link only is a combination of the media distribution system and the FLO technology. The FLO technology is the ability to deliver a rich variety of content choice to consumers while efficiently utilizing spectrum as well as effectively managing capital and operating expenses for service providers. The details of the MediaFLO™ mobile multimedia multicast system are available in Chari, M. et al., “FLO Physical Layer: An Overview,” IEEE Transactions on Broadcasting, Vol. 53, No. 1, March 2007, the contents of which, in its entirety, is herein incorporated by reference.
FLO technology was designed specifically for the efficient and economical distribution of the same multimedia content to millions of wireless subscribers simultaneously. Also, the FLO technology was designed from the ground up to be a multicasting network, which is overlaid upon a cellular network. It does not need to support any backward compatibility constraints. Thus, both the network infrastructure and the receiver devices are separate from those for the cellular/PCS network. Moreover, as the name suggests, the technology relies on the use of a forward link (network to device) only.
FLO enables reducing the cost of delivering such content and enhancing the user experience, allowing consumers to “surf” channels of content on the same mobile handsets they use for traditional cellular voice and data services.
MediaFLO™ technology can provide robust mobile performance and high capacity without compromising power consumption. The technology also reduces the network cost of delivering multimedia content by dramatically decreasing the number of transmitters needed to be deployed. In addition, MediaFLO™ technology-based multimedia multicasting complements wireless operators' cellular network data and voice services, delivering content to the same cellular handsets used on 3G networks.
The MediaFLO™ wireless system has been designed to broadcast real time audio and video signals, apart from non-real time services to mobile users. The system complements existing networks and radically expands the ability to deliver desired content without impacting the voice and data services. Operators can leverage the MediaFLO™ system to increase average revenue per user (ARPU) and reduce churn by offering enhanced multimedia services. Content providers can take advantage of a new distribution channel to extend their brand to mobile users. Device manufacturers will benefit from increased demand for multimedia-enabled handsets as consumer appetite grows for the rich content provided through MediaFLO™ systems.
The MediaFLO™ service is designed to provide the user with a viewing experience similar to a television viewing experience by providing a familiar type of program-guide user interface. Users can simply select a presentation package, or grouping of programs, just as they would select a channel to subscribe to on television. Once the programs are selected and subscribed to, the user can view the available programming content at any time. In addition to viewing high quality video and audio content and IP data, the user may also have access to related interactive services, including the option to purchase a music album, ring tone, or download of a song featured in a music program. The user can also purchase access to on-demand video programming, above and beyond the content featured on the program guide.
The respective MediaFLO™ system transmission is carried out using tall and high power transmitters to ensure wide coverage in a given geographical area. Further, it is common to deploy 3-4 transmitters in most markets to ensure that the MediaFLO™ system signal reaches a significant portion of the population in a given market. During the acquisition process of a MediaFLO™ system data packet several determinations and computations are made to determine such aspects as frequency offsets for the respective wireless receiver. Given the nature of MediaFLO™ system broadcasts that support multimedia data acquisitions, efficient processing of such data and associated overhead information is paramount. For instance, when determining frequency offsets or other parameters, complex processing and determinations are required where determinations of phase and associated angles are employed to facilitate the MediaFLO™ system transmission and reception of data.
To achieve good receiver performance and high spectral efficiency of multimedia multicasting in a mobile communication environment, the FLO physical layer uses Orthogonal Frequency Division Multiplexing (ODFM) as the modulation technique. Inside an ODFM symbol, a Wide-area Identification Channel (WIC) spans one OFDM symbol and is transmitted at the first ODFM symbol index in a superframe. It follows the first Time Division Multiplexing (TDM) Pilot ODFM symbol. This is an overhead channel that is used for conveying the Wide-area Differentiator (WID) to the FLO receivers. The Local-area Identification Channel (LIC) spans one ODFM symbol and is transmitted at the second ODFM symbol index in the superframe. It follows the WIC channel ODFM symbol. This is an overhead channel that is used for conveying the Local-area Differentiator (LID) information to the FLO receivers.
The values of WID and LID constitute a part of the scrambling sequence that is used for the scrambling of both the wide and local area Overhead Information Symbols (OIS) and the data fields. Without the values of the WID and the LID, it is not possible to descramble either the OIS or the data fields.
Channel model is the model that describes the phenomena that affect the transmitted information along its path to the receiver. These phenomena may change transmitted frames completely. In order to avoid incorrect or incomplete reception there is an equalizing stage at the receiver that creates a model for the channel and equalizes its effect. The received data sequence, as schematically represented in FIG. 1A, can be represented by the equation r(t)=h(t)*x(t), where r(t) is the received data sequence, h(t) is the channel effect, and x(t) is the descrambled transmitted data sequence. The role of the equalizer is to estimate the channel effect h(t) continuously in order to get the actual descrambled transmitted data sequence x(t). For this purpose FDM pilots are typically needed.
The FDM pilot symbols are descrambled and sent within the OIS and data frames symbols inside the superframe. To find the values of FDM symbols, it is desirable to get the values of WID and LID, which become distorted by the channel effects. The WIC and LIC symbols do not contain FDM pilots so a channel model typically cannot be constructed for these symbols. Accordingly, there remains a need to derive WIC and LIC estimation in MediaFLO™ mobile multimedia multicast systems.